基于形状因子的辐射地板传热量计算等效热阻模型

An Equivalent Thermal Resistance Model to Calculate the Heat Transfer of Radiant Floor Heating and Cooling Systems Using Shape Factor

对辐射地板传热过程进行分析,提出了基于形状因子的辐射地板传热量计算等效热阻模型.为了验证简化模型的合理性,采用数值模拟计算结果进行验证,并与标准手册中采用的简化模型计算结果进行对比分析.结果表明,当管间距变化范围为50~250mm,换热管上端填充层厚度变化范围为25~65mm及热水平均温度变化范围为25~45℃时,ISO标准幂函数计算模型、ASHRAE手册平面肋片模型及地暖设计手册等效热阻模型计算结果与数值模拟计算结果相对误差均较大,最大分别为20.2%,30.4%和22.8%,而本文提出的基于形状因子的等效热阻模型计算结果与数值模拟计算结果相对误差较小,最大不超过3%;当管间距变化范围为50~200mm,换热管上端填充层厚度变化范围为15~55mm及冷水平均温度变化范围为10~20℃时,ISO标准幂函数计算模型、ASHRAE手册平面肋片模型及地暖设计手册等效热阻模型计算结果与数值模拟计算结果相对误差也均较大,最大分别为80.1%,17.7%和16.8%,而本文提出的基于形状因子的等效热阻模型计算结果与数值模拟计算结果相对误差较小,最大不超过2%.

An equivalent thermal resistance model for the heat transfer calculation of radiant floor based on shape factor was developed in this study. The proposed model was verified by numerical simulation, and compared with the data from the universal single power function of ISO standard, the fin model in ASHARE handbook, and the equivalent thermal resistance model in design handbook. The heat transfers obtained by the numerical simulation disagreed significantly with the existing methods including the universal single power function of ISO standard, the fin model in ASHARE handbook, and the equivalent thermal resistance model in design handbook. The maximum error rates were 20.2 %, 30.4 %, and 22.8 %, respectively, when the tube space ranges from 50 to 250 mm, the thickness of fill layer above pipe ran- ges from 25 to 65 mm, and the average hot water temperature ranges from 25 to 45 ℃. On the other hand, the maximum difference of the heat transfer predictions between the proposed model and the simulation software was less than 3%. When the tube space ranges from 50 to 200 mm, the thickness of fill layer above pipe ranges from 15 to 55 mm, and the average cold water temperature ranges from 10 to 20 ℃, the maximum error rates of the heat transfer predictions between the numerical simulation and the existing methods were 80.1 %, 17.7 %, and 16.8%. On the other hand, the heat transfer predicted by the pro- posed model showed less than 2 % of difference from that of the numerical simulation.